It's an Acer 5520 and when it shuts off the power button flashes every 2 seconds. Sometimes I can remove the battery and get a restart...usually not right away. It happens whether the AC is plugged in or not.

1 Disconnect the battery and the charger2 Let it sit for 1-2 minutes.3 Press and hold down the power button for 30 seconds.4 Connect the charger (don't connect the battery yet) and try to start by pressing the power button.

If the system turns itself off after a certain amount of time and fails to turn on after that, then it can be due to overheating.

Actually the motherboard will try to turn it off to prevent any damage to the processor.

You can try to clean the cooling vents using a can of compressed air or a vacuum cleaner (make sure to turn off the system and disconnect battery and charger before you try this).If the processor heatsink/fan assembly is clogged with dusts, it can cause this problem.

You need to make sure that the processor heatsink/ fan assembly is clean of any dusts.